The manufacture of semiconductor devices is an equipment-intensive venture. The expense of purchasing, maintaining, and repairing production equipment adds significantly to the final cost of semiconductor devices. Equipment technicians are employed to maintain and keep equipment in working order, which minimizes unexpected failures and decreases downtime. Equipment must be removed from production for both maintenance and repair, and increasing the percentage of time equipment remains in production decreases costs and is a goal of equipment engineers and semiconductor fab managers.
Production of semiconductor devices requires photolithographic processing to provide repetitive, patterned features on the surface of the semiconductor wafer. During photolithography, a semiconductor wafer is coated with photosensitive photoresist (resist), then the resist is exposed to a light pattern to alter the chemical makeup of the resist. After exposure of the resist to light, the coated wafer is rinsed with a developer to leave a pattern of resist material over the wafer surface. The patterned photoresist can then be used to etch underlying materials.
To coat the wafer surface with photoresist, a coater track system can be used. A number of photoresist track systems are produced by various manufacturers, for example the POLARIS® P2000 lithography coat system, available from FSI International of Allen, Tex. To coat the wafer with photoresist, a semiconductor wafer is placed onto a chuck within the track system. The chuck spins the wafer, and photoresist is applied to the top of the wafer through a dispensing nozzle which is part of a bowl rinse hardware assembly. The rotation of the wafer results in a uniform, thin coating of resist over the wafer surface. Any excess photoresist is removed from the wafer by centrifugal forces during application, and is contained within a coater cup.
During repeated photoresist applications to a number of different wafers, a buildup of excess resist on various interior surfaces of the coater process bowl system can result, which must be cleaned away. A coater process bowl system typically comprises an automated bowl rinse hardware assembly which periodically rinses the coated surfaces of the coater process bowl system to prevent buildup of excess photoresist. The FIG. 1 cross section depicts a coater process bowl system 10. A deflector 12 is spaced from a baffle 14 to provide a gap 16 which opens to an accumulator 18. The deflector 12, baffle 14, and accumulator 18 together form a “coater cup” assembly. The bowl rinse hardware assembly comprises various structures such as a flange 20, an inlet subassembly 22, a backing plate 24, and a nozzle mount 26 having cleaning nozzles 28 attached thereto. In a typical system, the accumulator has a diameter of about 15.5 inches and the nozzle mount has a diameter of about 5.125 inches.
During coating of the wafer, excess photoresist is forced from the spinning wafer and onto the interior surface of the deflector 12. After coating a number of wafers, the deflector 12 is cleaned by ejecting (outputting) solvent 30 (FIGS. 1 and 2) from the nozzles 28 and onto the deflector 12. The track dispenses photoresist onto the wafer using a separate nozzle (not depicted) while the cleaning nozzles 28 dispense a photoresist cleaning solvent such as propylene glycol monomethyl ether acetate (PGMEA). In a typical configuration, the nozzle mount 26 has six cleaning nozzles attached thereto, as depicted in FIG. 2. The solvent rinses the excess resist from the interior surface of the deflector 12, and the solvent and resist flow down the deflector 12 through the gap 16 provided the deflector 12 and a baffle 14, and finally into the accumulator 18 where it is drained away into a larger waste collection system for disposal or recycling.
As depicted in FIGS. 1 and 2, solvent 30 is ejected from nozzles 28 using a flat, fan spray pattern. As depicted in FIG. 1, the fan spray exits the nozzle at a slight upward incline of about 15° to contact the deflector 12. Further, as depicted in the cross sectional top view of FIG. 2, the solvent 30 exits the nozzle horizontally at an angle 32, for example at an angle of about 90°. The solvent pattern should provide a continuous circle around the interior surface of the bowl so that interior locations of the deflector 12 are rinsed.
After several photoresist dispenses, the gap 16 provided by the deflector 12 and the baffle 14 can become blocked with resist, which can prevent the proper exhaust of resist and solvent through the gap and into the accumulator 18. As such, the coater process bowl assembly is periodically disassembled and sent out for cleaning. Manual cleaning is required after 96 continuous hours of use, and requires removal of the coater track system from production.
A coater process bowl system requiring less manual cleaning than previous designs would have reduced downtime, would require less technician time, and would therefore be less expensive to operate, thereby resulting in decreased production costs.